A touchscreen consists of a display and a sensor for user input, and it can be considered as a touch-sensitive surface. As a combined input and output device, a touchscreen creates the feeling of very direct control of a computer by simply touching the screen. In addition, the touch-sensitive surface can be used without a display, and in this case, it is known as a touchpad.
For interacting with a touchscreen, users commonly use a finger of the hand or a stylus. Depending on the technology, the position of the finger or stylus on the touchscreen is determined by capacitive sensing or resistive sensing. The user can trigger touchscreen events through gestures, e.g., by tapping on the touchscreen with the finger or by dragging the finger over the touchscreen. The touchscreen events causes the system to execute functions, usually accompanied by a change in the content displayed on the touchscreen.
Multi-touchscreens can recognize multiple points of contact simultaneously and hence are able to detect several fingers of the user. This increases the number of possible gestures. A well-known example is the possibility to zoom in to images or text by touching the surface with two fingers and moving them apart. An overview of known gestures can be found at the URL: http://www.lukew.com/touch/(Villamor, Craig/Willis, Dan/Wroblewski, Luke: Touch Gesture Reference Guide).
Owing to their small size, smartphones and smartwatches, i.e., phones and watches with computer functionality, have very limited space to display buttons, icons, or other control elements on the touchscreen. Therefore, for saving space on the touchscreen, it is advantageous if several different functions can be triggered by the same button, icon, or control element using different gestures. The more distinguishable gestures are available, the greater is the number of different functions that can be accessed directly from a single location on the touchscreen without further interposed interaction steps.
Smartphones and smartwatches usually are equipped with sensor devices. Common sensors include an acceleration sensor, i.e. accelerometer, a gyroscope, and a magnetometer. Each of these sensors has physical limitations and disadvantages. Therefore, a known approach involves combining several sensors to compensate for the disadvantages of individual sensors.
From prior art, it is known that functions can be triggered by shaking the smartphone or by tapping on the smartphone housing, which is detected by the acceleration sensor. In U.S. Pat. No. 7,671,756 B2, entitled “Portable electronic device with alert silencing”, this gesture is applied to stop an audible alarm. Furthermore, an alternative is described that operates without an accelerometer but instead uses the touchscreen, which is intended to detect non-specific smacks. Concurrent use of the touchscreen and the accelerometer is not intended.
U.S. Pat. No. 8,125,312 B2, entitled “System and method for locking and unlocking access to an electronic device”, describes how to lock and unlock a smartphone with knock patterns. An acceleration sensor is used for this purpose, and the touchscreen is not needed. Optionally, the user can enter a conventional text password using an onscreen keyboard. This is achieved through a second, independent step.
The patent application US 2011/0187652 A1 “Bump suppression” describes a method aiming to reduce user input misinterpretations. For this purpose, the system checks whether a conventional input, e.g., a tap on the touchscreen, generates a matching shock or tremor that can be detected by a built-in acceleration sensor. These shocks or tremors are short vibrations with very small amplitudes. The information from the touchscreen and from the acceleration sensor are combined solely for distinguishing between intentional and unintentional vibrations. In particular, no new gestures are introduced for the touchscreen.
In the paper “Goel, Mayank/Wobbrock, Jacob O./Patel, Shwetak N.: GripSense: Using Built-In Sensors to Detect Hand Posture and Pressure on Commodity Mobile Phones. Proceedings of the ACM Symposium on User Interface Software and Technology (UIST '12). Cambridge, Mass. (Oct. 7-10, 2012). New York: ACM Press, pp. 545-554. URL: http://faculty.washington.edu/wobbrock/pubs/uist-12.pdf”, methods are presented to determine the pressure on a touchscreen as soon as it is touched by the user. In addition, an attempt is made to identify the hand posture. For this purpose, among others, a gyroscope is used to detect minimal and unintentional rotations that occur as the user interacts with the smartphone using just one hand and the thumb. Only conventional and known gestures are described. The paper narrows down to determine additional information about the hand posture for improving input quality.
The patent application US 2011/0254792 A1 describes a method for enhanced control of an application program, which works like a data recorder. A first conventional tap on the touchscreen starts recording and monitoring of acceleration and/or gyroscope data. A second tap on the touchscreen stops the recording. The spatial movement of the smartphone between the first and second taps is interpreted as a gesture. Alternatively, the recording of sensor data can take place so long as a finger touches the touchscreen at a specific location, known as “touch and hold” or “long press.”
The patent application US 2010/0060475 A1 describes a touchscreen with a proximity sensor that allows users to interact with an application program by holding a finger over the touchscreen without touching it. Finally, patent application US 2012/0092332 A1 describes a method to control in three dimensions an image displayed on a screen. This is achieved by tilting the device and performing a conventional drag gesture with a finger.